Laser-inherent porosity defects in additively manufactured Ti–6Al–4V implant: Formation, distribution, and effect on fatigue performance
Abdul Azeez Abdu Aliyu, Chedtha Puncreobutr, Surasak Kuimalee, Thanawat Phetrattanarangsi, Thanachai Boonchuduang, Pariwat Taweekitikul, Chinnapat Panwisawas, Junji Shinjo, Boonrat Lohwongwatana
Abstract
Porosity defects are inherently present in Ti–6Al–4V (Ti6-4) parts produced using additive manufacturing (AM) methods like laser powder-bed fusion (LPBF). This work aims to investigate different laser-inherent porosity defects at various LPBF parameter settings and assess their impact on the fatigue behaviour of Ti6-4 implants processed by LPBF. The presence of LPBF-inherent porosity defects with different shapes and sizes was established using microstructural examination and X-ray micro-CT analysis. These mostly comprise lack-of-fusion porosity (LoFP), gas-entrapped porosity (GeP), and pores-induced microcracks. Volumetric porosity defects were seen to range from 1.9 × 10 4 to 9.52 × 10 5 μm 3 . The L-1 specimen exhibited the lowest defect, while the L-6 specimen displayed the largest number of defects. While LoFP defects predominate in L-6, there was a notable presence of GeP defects in the specimens processed using the factory default condition (L-D). Upon examination of the majority of specimens, GeP and LoFP coalesced to form clusters, leading to the formation of pores-induced microcracks. This ultimately leads to a decrease in fatigue performance. By maintaining the power at the default setting and increasing the scan speed by 8% of the default value, a specimen (L-1) with minimal porosity defects and superior fatigue performance is achieved. L-6 exhibits defects with significant dimensions and irregular form. Consequently, it displays inferior fatigue characteristics. • X-ray Computed tomography and Archimedes density approaches were used to evaluate the laser-inherent porosity defects. • The defects were detected at various parameter settings according to their size, quantity, and geometry. • The primary laser-inherent porosity defects influencing fatigue behaviour were identified. • Cracks initiating sites including surface and subsurface regions were ascertained.